Sergeant Nicolas Verendrye

A former physician who has turned his skills to the ceaseless conflicts of western Immoren, Sergeant Nicolas Verendrye is highly esteemed by those under his command. Verendrye has found his place in the bloody press of melee, employing his medical expertise to keep his men standing and using his keen battlefield acumen to lead them to victory.

Steelhead Halberdiers - This seems the obvious choice since most of the Sergeant's abilities now affect them and only them. Possibly effective with Constance Blaize to provide an additional ARM boost on her feat turn.

Field Medic is still useful for a lot of Merc units who don't already have Tough, including Warcasters/Warlocks. Handy if you don't have other options available, though Verendrye is rather squishy without his Halberdier buddies - even more so now that he no longer has Tough himself.

In an Irregulars army with pirates, he can give Sea Dog Pirates tough without having to spend a coin from Lord Rockbottom. Combine with Doc Killingsworth and Bosun Grogspar and you've used up all your free solos!

You can gain the Flank bonus vs knocked down/stationary models (refer to the latest Errata).

Melee range is measured from your front arc so you cannot trigger Flank on models in your back arc.

The target enemy doesn't need to be in the Flanker's LOS, just their melee range.

Most of the time if something is in your melee range then it is so close it's in your LOS too, and the difference is meaningless.

But if you have 2" reach and you're jammed up in B2B with a bunch of closely-spaced enemies, you'll find your LOS is blocked. In this case, you might be able to trigger Flank on an enemy model that is "hiding" behind that front row of jammers, even though you don't have LOS to it.

Flank is not tied to a specific weapon, so Mount attacks and Power Attacks can benefit as well.